Multimodal Should Fail with Specific Message when no Transit is Available

`http://localhost:8002/route?json={%22id%22:%22foo%22,%22locations%22:[{%22lat%22:40.520061,%22lon%22:-76.500497},{%22lat%22:40.520061,%22lon%22:-76.499366},{%22lat%22:40.520061,%22lon%22:-76.32578}],%22costing%22:%22multimodal%22}`

i was testing with the above to make sure that multimodal costing still worked after making a fix for #1172

since i knew this location has no transit data i expect it to fail with the error about destination too far from transit location. instead it fails with now path. when i set costing to pedestrian it doesnt fail at all. looking at the code it seems to fall through the multimodal algorithm without hitting the destination exception and instead returns an empty path.

Start with the multimodal route request in the issue and compare its behavior with the pedestrian request, keeping the interaction with #1172 in mind. Trace the multimodal algorithm's no-transit path and identify why it returns an empty path instead of the destination-too-far-from-transit error. Done means the supplied no-transit request fails with that specific message.

Written by the indexing model from the issue text.